Exchange of Materials

Question 1

Surface Area to Volume Ratio

Answer 1

The amount of surface area per unit volume of an object or collection of objects

Question 2

Cell Size

Answer 2

• Most cells are incredibly small, between 10 and 15 micrometres (µm) in diameter.
• A micrometre is one-thousandth of a millimetre.
• There is a limit to how big a cell can be. All the requirements and products of a cell must pass across the membrane that surrounds the cell.

Question 3

Factors affecting material exchange

Answer 3

Factors affecting the exchange of materials across the cell membrane include..

• Surface area to volume ratio
• Concentration gradient
• Physical and chemical nature of materials being exchanged

Question 4

Surface Area

Answer 4

• The relationship between the surface area of the cell and the volume is very important.
• As the apple is cut in half the surface area increases.
• If you continue to cut the apple into small
  pieces, the surface are to volume ratio of
  the pieces gets bigger and bigger.

Question 5

Concentration Gradients

Answer 5

• A concentration gradient results from the unequal distribution of particles.
• Particles may move along or against their concentration gradient.

Question 6

Physical and Chemical Nature

Answer 6

Physical: the size of the particle being exchanged e.g. glucose needs channels

Chemical: refers to the polarity of ions and how they are unable to move freely.